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RB25/VG30 hybrid highflow Turbo?

riceline

By riceline,
in Engines & Forced Induction

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riceline Community Regular

riceline

Posted
Posted

Hey all.

I have purchased a RB25 S2 turbo that I am going to have highflowed along with a 360 Deg Thrust bearing put in. This will be going onto my RB31DET.

My question is. I know that people put the VG30 exhaust housing on the RB25 turbo for a performance increase. Would it be worthwile/feesable for me to put a VG30 exhaust housing on the 25 turbo before it is highflowed?

In my head it seems like an easy way to get just a Little more power out of it. While possibly giving it a little more punch from the 3L bottom end.

I know that this type of set up may cause surging and be a little laggy on a 2.5L but I think it should be fine on a 3L.

Thanks guys

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Cubes Grand Master

Cubes

Posted
Posted

If anything fitting the VG30 exhaust housing to the stock RB25 CHRA will decerease the chances of surge as it will shift spool to a later rpm where the engine is able to consume more air.

Give it ago. Maybe do a before and after power run just to give us all an indication how the larger a/r reacts with the 3ltr. :rofl:

I sure would be interested.

discopotato03 Grand Master

discopotato03

Posted
Posted

In std form the VG 30 ceramic BB turbo or its exhaust housing on the std RB25 ceramic BB turbo could work ok up to the ceramic turbines speed limit . These were fitted to a 3L VG 30 after all .

Be wary of bush bearing hybrids using the VG/RB housings , the ceramic turbine is the only one that really suits them properly . Boring the exhaust housing out butchers the nossle section and it can't work properly . Unfortunately turbos of this size need to run at high shaft speeds to move enough air , and the bush bearing and thrust plate / collar affair won't stand this for too long . Apart from the above options there are no cheap answers .

Cheers A .

riceline Community Regular

riceline

Posted
  • Author
Posted

Disco: - I am getting the Rb25 turbo highflowed - that means 360degree thrust bearing. new seals - steel wheels - bored out etc etc. I want to put the VG30 exhaust housing on the turbo to give it even more go again.

Abused: Most of the reasons as above. I want it to go straight onto the car with minimal fuss. I'm not interested in a stupidly big turbo that takes ages to spool. This is my daily driver. I drive it to work and back home. Some weekends me and my girlfriend go away in it. Every now and then it will be off to the drags/track. Thats about it. The fact that it looks 100% stock as well. The truth is a Std high flow puts out 450hp. Hopefully just putting this extra bit on gives 470-520 hp (hope/guess) that is more than enough with my other mods for the streets.

Thanks guys please keep the info coming

Roy Grand Master

Roy

Posted
Posted
Disco: - I am getting the Rb25 turbo highflowed - that means 360degree thrust bearing. new seals - steel wheels - bored out etc etc. I want to put the VG30 exhaust housing on the turbo to give it even more go again.

Whilst i think plan bearing turbos are fine, if you have a ball bearing turbo, i dont see the sense when getting it rebuilt going to a 360deg thrust bearing setup? Other then expense of course, but there are places aroudn that do BB as well and are only a $200 more:) (approx)

riceline Community Regular

riceline

Posted
  • Author
Posted

Cubes: That's the hope :) a skanky little 250rwkw :rofl: (or more if possible :P)

I was recommended the 360 deg thrust bearing setup as it should make more reliable power. That's really why I am/was going with it. The other option was a 270 deg thrust bearing that would be cutting down the life of the turbo and the power.

I will ask about getting it BB set up as well.

Thanks for the advice roy.

Cubes Grand Master

Cubes

Posted
Posted

Depends how much you can get it all for.. If you are buying from a jap wrecker you are better off getting your current turbo highflowed.

A little while back when I had the RB20t jap wreckers were asking around $700 for an RB25 turbo & $500 for a VG30DET BB turbo.

riceline Community Regular

riceline

Posted
  • Author
Posted

hey mate

I picked up a blowen R33 S2 turbo for $100

Have seen a few places that sell the rear housing for about $100-150

The highflow job with the 360deg thrust bearing is costing aprox $1300

After all of this I will still have my current RB25 turbo to bolt onto my mates R32. So that will bring the cost down a little

  • 3 weeks later...
ABuSD Veteran

ABuSD

Posted
Posted

doesnt seem worth it, maybe pay a little extra and get a garret 450-500hp roller??

I understand now why u wouldnt want to thow a huge turbo on it. My mates got heaps of power with a big turbo and its not as driveable as u probably want it to be!

All the best anyways!!!

Rexbo Apprentice

Rexbo

Posted
Posted

Who is doing this stuff for you? The whole 270 degree vs 360 degree thrust bearing durability argument is kinda pointless if the shop that's doing it for you doesn't low-speed and high-speed balance the rotating assemblies for you, and you're going to be spinning it past its efficiency range anyways. Especially with the ceramic wheels, overspinning will lead do very premature failure. I'd say, save your money and get a real ball bearing turbo (not a single ball bearing unit with a thrust bearing), that is properly matched to the engine. You know we DO make turbos smaller than a GT40R... And it seems that for the prices you are saying, you could be coming close to just buying a new gt28R or gt25R with the t25 flange that will bolt right up anyways.

I'd say unless the shop you're doing this at is VERY reputable with turbos, you're only buying a temporary solution.

PRO_32 Proficient

PRO_32

Posted
Posted
And it seems that for the prices you are saying, you could be coming close to just buying a new gt28R or gt25R with the t25 flange that will bolt right up anyways.  

I'd say unless the shop you're doing this at is VERY reputable with turbos, you're only buying a temporary solution.

Rb25 and vg30 turbo's are T3 flanged and we have pretty reputable shop's doing this sorta stuff out here eg. GCG..

  • 4 months later...
Cubes Grand Master

Cubes

Posted
Posted

I've got both a vg30 and r34 gtt turbo that i'm measuring up.

It appears the elbow from the r34 turbo will indeed bolt up to the vg30 turbo. The RB20DET elbow definitely won't.

I am unsure of the R33 rb25det turbo's elbow.

I've also discovered as have some others, that the R34 GTT turbo has the exact same size turbine housing as the VG30DET turbo.

sThe only difference between the two is that the R34 turbo runs a slightly larger compressor BUT it does have a anti-surge ring or what ever its called located in the snout which reduces efficiency.

Stock vs stock I'm not really sure which is better.

Larger compressor with an anti-surge ring or slightly smaller compressor without the surge ring.

Could you please do me a favour and measure the r33 rb25det turbine housing as the following pic illustrates and post the results?

Even just by using a ruler with a sharp eye will be good enough. :P

For example the cross section width of the rb20det turbo is ~45mm.

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